The present invention is related to riveting and in particular to forming riveted pivot joints including a desired amount of clearance.
It is common in manufacturing to form a joint in which a rivet serves the dual purposes of both fastening two or more parts together and acting as a pivot shaft, as in pliers joints, scissors joints, wire cutters, or various types of pinions. Rivet tension or clearance in such a joint is a factor in determining the amount of friction between two or more pivotally interconnected members. In a joint in a tool such as pliers, it is usually desired to have two or more members in pivotal contact with one another, but not held so tightly together that friction interferes with their use, nor with so much clearance that the parts of a tool feel loose or sloppy with respect to each other. In the case of scissors or wire cutters, looseness may detract from the effectiveness of the tool in its primary cutting function. Such a tool with a loose or sloppy rivet joint is commonly perceived as having low quality.
The most widely used method of controlling the amount of tension or clearance in rivet joints, particularly in tools whose parts pivot with respect to each other, is manual adjustment. That is, after a rivet joint has been formed by machinery, hand tools are used to tighten or loosen the joint as necessary. This often results in inconsistent quality of pivot joints or imperfections in the appearance of a rivet head.
What is needed, therefore, is an improved method and apparatus for automatically forming rivets to form joints having a very small, but accurately established, amount of clearance between the parts riveted together, so that the parts are pivotally movable with respect to one another, with neither excessive friction nor excessive clearance, and without the need for manual adjustment.